This invention relates generally to the analysis of semiconductor integrated circuits and, in particular, to a man-machine interface for manipulating a plurality of images representative of a surface of a deconstructed semiconductor integrated circuit (IC) to extract design and layout information therefrom.
In the semiconductor industry it is often necessary to physically analyze semiconductor integrated circuits (ICs) for the purposes of product reliability assurance, design validation and identification of device structural patterns. ICs are analyzed to extract design and/or layout information therefrom. This process is known as reverse-engineering. Reverse-engineering is also part of the test and development process in the manufacture of ICs on a large scale. In general, a vast amount of time and manual labor is required to reverse-engineer an IC.
An IC is a monocrystaline silicon die upon which a large number of transistors and other electronic components have been fabricated and interconnected to form a useful circuit. During manufacture, each die is part of a larger silicon wafer substrate which facilitates handling and simultaneous processing of a plurality of ICs.
The IC fabrication process includes: doping the silicon substrate to change its conductive properties and building up a sequence of layers onto the silicon substrate using different techniques. Doping layers are created using ion implantation. Diffusion layers are created by depositing dopants on top of a substrate and heating the wafer. With each deposition layer, different materials are deposited and selectively removed by selective etching in accordance with a predetermined pattern. Components manufactured on the silicon wafer span multiple layers. Oxide layers are used for insulation. Deposited metal layers are used to interconnect individual terminals of the components so formed.
It is the identification of these components and the interconnections provided by the metal layers that provides base information from which the design and/or layout of an IC can be extracted and verified.
In reverse-engineering a sample IC, the die is deconstructed. The IC sample die is subjected to a progressive layer-removal sequence utilizing an exacting series treatment, such as acid etchants, each of which is specifically chosen to remove a single layer at the time. Other deconstructive treatments include dry etching, polishing, etc. Using such treatments, interconnecting metal layers, polycrystalline silicon layers, oxide layers, etc. are removed step-by-step. At each deconstructive step the surface of the partly deconstructed IC is inspected.
Inspection techniques include the use of: optical microscopes, scanning electron microscopes, and other surface inspection equipment. In general, the scanning electron microscope is accurate but is expensive to own and operate. Optical microscopes can be used in brightfield, contrast interference and darkfield modes of illumination.
In the brightfield or contrast interference modes, the physical extents of the components on the die are distorted by fringe effects. These fringe effects can be interpreted by an experienced human analyst but require vast amounts of computation for analysis by a computer.
A xe2x80x9cMETHOD OF EXAMINING MICROCIRCUIT PATTERNSxe2x80x9d is described in the U.S. Pat. No. 4,623,255 which issued Nov. 18, 1986 to Suszko. The method involves photographing an IC die in between deconstructive steps. Film transparencies are printed and used by an engineer analyst to extract design and layout information from the photographed IC. While the teachings of Suszko have merit, design and layout extraction are impeded by the handling and cross-correlation of the bulky transparencies.
Another xe2x80x9cAUTOMATED SYSTEM FOR EXTRACTING DESIGN AND LAYOUT INFORMATION FROM AN INTEGRATED CIRCUITxe2x80x9d is described by Yu et al. in U.S. Pat. No. 5,086,477 which issued Feb. 4, 1992. A digital camera and a controlled stage are used to capture images in overlapping tile fashion after each deconstructive step. The captured digital images are stored in a computer memory and reassembled into image-mosaics based on the overlap at the borders of each tile image. Yu et al. describe pattern matching performed on an image-mosaic of a deconstructive step, and points out the difficulties involved in extracting layout information from the tile images. The automated system to Yu et al. appears to be suitable for extracting design information from complex ICs that are difficult to reverse engineer. To accomplish this, xe2x80x9ccellxe2x80x9d libraries are built. The cell libraries contain images of specific arrangements of components that are known to perform a specific function.
The cell libraries are used for automated pattern matching in order to facilitate reverse engineering of Application Specific Integrated Circuits (ASICs), for example. However, Yu et al. fail to describe how multiple image-mosaics, each representing a different step in the deconstruction of an IC, are manipulated in order to extract design and layout information concurrently therefrom. Concurrent analysis of image-mosaics is desirable because individual components fabricated on the silicon wafer may span multiple layers.
There is therefore a need for a man-machine interface that enables manipulation of multiple images of an IC to facilitate concurrent extraction of design and layout information therefrom.
It is an object of the invention to provide a man-machine interface adapted to facilitate feature recognition and analysis across multiple images representative of one or more surfaces of a semiconductor integrated circuit (IC).
It is another object of the invention to provide a man-machine interface that supports multiple views, each view displaying a portion of an image-mosaic and one of a group of multiple lock-step cursors.
In accordance with one aspect of the invention a man-machine interface for analyzing image-mosaics is presented. The man-machine interface includes a display area, a system pointer, a plurality of mosaic-views and a corresponding plurality of lock-step cursors. The image-mosaics are aligned to a sample coordinate space. The display area defines a display coordinate space and the system pointer has a position with respect to the display coordinate space. Each one of the plurality of mosaic-views has view-boundaries in the display coordinate space and displays one of the plurality of image-mosaics. Each lock-step cursor has a position in the display coordinate space and shares positional coordinates in the sample coordinate space with all of the other lock-step cursors. The system pointer, when positioned within at least one view-boundary, takes on a representation of a master-cursor which controls cursor-events. Lock-step cursors are displayed in the other views at the position of the master-cursor in the sample coordinate space. The image-mosaics are, for example, representative of a deconstructed semiconductor integrated circuit (IC) sample.
According to another aspect of the invention, the man-machine interface further includes a navigation window having view-boundaries in the display coordinate space and displaying a low magnification image representative of the IC sample. The navigation window also enables the selection of at least one area-of-interest displayable in a plurality of mosaic-views.
The invention also provides a method of analyzing image-mosaics that are scaled and aligned to a sample coordinate space. The method comprises steps of displaying an area of interest of respective ones of a plurality of the image-mosaics within respective mosaic-views displayed on a display coordinate space of a man-machine interface used to analyze the image-mosaics. The method further comprises a step of tracing features of the IC across at least two of the mosaic-views using a master-cursor in a one of the mosaic-views and lock-step cursors in others of the mosaic-views. The master-cursor controls cursor events and the lock-step cursors are displayed within the other mosaic-views at a relative position of the master-cursor with respect to the sample coordinate space, provided that the relative position is within the respective display coordinate space of the other mosaic-views.
The image-mosaics are created, for example, by deconstructing a semiconductor integrated circuit (IC) sample. An area of interest of an image-mosaic is created using a slice creation tool to define coordinates on the sample coordinate space. The slice is preferably created by dragging a system pointer along a diagonal path to define a rectangular area of interest on a low resolution die photo of the IC sample. After the slice is created, image-mosaics to be displayed in mosaic-views of the area or interest are selected. The image-mosaics to be displayed in mosaic-views of the area of interest may be selected from a list of all image-mosaics associated with the slice, or selected automatically by the apparatus. When the master-cursor is removed from the one of the image-mosaics, the master-cursor becomes a system pointer on the display surface of the man-machine interface, and the lock-step cursors are erased from each of the other mosaic-views.
The invention further provides an apparatus for analyzing image-mosaics, the image-mosaics being scaled and aligned to a sample coordinate space. The apparatus comprises a workstation having a display area that defines a display coordinate space, and a pointing device that controls a system pointer that may be moved within the display coordinate space. A memory for storing a plurality of mosaic-views having respective view-boundaries when displayed in the display coordinate space, each mosaic-view displaying at least a portion of one of the image-mosaics. An algorithm displays a lock-step cursor within each of the mosaic-views, the lock-step cursors sharing positional coordinates with respect to the sample coordinate space. When system pointer is moved across a view-boundary into a one of the plurality of mosaic-views by manipulation of the pointing device, the system pointer is displayed as a master-cursor that controls cursor events and the lock-step cursors are displayed within other mosaic-views at a relative position of the master-cursor with respect to the sample coordinate space, provided that the relative position is within the respective display coordinate space of respective ones of the other mosaic-views.
When a cursor event indicating cursor movement is detected, the means for displaying converts coordinates of the system pointer in the display coordinate space to coordinates in the sample coordinate space and performs an iterative process to send the coordinates in the sample coordinate space to each of the other mosaic-views, if the coordinates of the system pointer in the display coordinate space are within a one of the mosaic-views.
The advantages of the system include increased production and reduction of analyst fatigue due to the facilitation of feature matching across image-mosaics and the avoidance of transposition errors while tracing components from one image-mosaic to another.